Girdle widths on diamond grading reports

[pyramid]

When do labs specify a diamond width as say medium as opposed to a range of widths e.g. extremely thin to medium?

 

[pyramid]

Thank you GlitterGal.

I think I was meaning more where people write here their girdle is Extremely thin to thin and they are asked to check how much of the area is Extremely thin.

Why is the girdle not noted as Thin if only a tiny part is extremely thin or Extremely thin if most of the girdle is extremely thin.

I have also noticed on GoodoldGold site where a GIA certificate will say a range which is say thin to medium and then when Jonathan has done all his calculations with the sarin report he will list girdle as perhaps just medium. Is this the average meaning less of the girdle is thin for instance.